Diochus octavii Fauvel, 1877

Huang, Tian, Zhou, Yu-Lingzi, Janák, Jiří & Zhou, Hong-Zhang, 2024, Four new species and a key to Australian species of the genus Diochus Erichson (Coleoptera: Staphylinidae, Staphylininae, Diochini), Zootaxa 5512 (3), pp. 343-372 : 364-366

7. Diochus octavii Fauvel, 1877

( Fig 8 )

Fauvel, 1877: 235 (Type locality: Australe, Victoria); Fauvel, 1878: 535 ( Australia); Olliff, 1887: 472 (characters; Australia); Bernhauer and Schubert, 1914: 319 (catalog); Bernhauer, 1920: 16 ( Australia); Lea, 1925: 220 (characters; Australia).

Type material examined. AUSTRALIA: Victoria: Holotype: male, “Victoria / Australie” (Fauvelʼs handwriting) // “Wu[?] – Bay” (Fauvelʼs handwriting) // “TYPE” (red, printed) // “ Diochus / octavii Fvl. ” (Fauvelʼs handwriting) // “ R.I.Sc. N.B. 17.479 / Coll. et det. A. Fauvel ” (printed) ( IRSNB).

Note. We examined the unique male type from the Fauvel collection ( IRNB). The specimen was remounted, glued on a new card plate, aedeagus and last abdominal segments were embedded in Euparal on a plastic plate placed at the same pin as the specimens together with the original small rectangular card plate. As Fauvel (1877) mentioned in the description “Un seul exemplaire” and the specimen was labeled as “TYPE” there is no doubt that it is a holotype of the species .

Measurements. BL = 4.47 mm, FL = 2.49 mm, HL = 0.69 mm, HW = 0.51 mm, EL = 0.19 mm, TL = 0.40 mm, PL = 0.89 mm, PW = 0.68 mm, EL = 0.85 mm, EW = 0.85 mm, SL = 0.63 mm.

Redescription. Body ( Fig 8A ) long, narrowed anteriorly and posteriorly, medium-sized. Body entirely dark brown to black, abdominal intersegmental membrane and abdominal segments VIII−X lighter, reddish brown. Legs yellowish brown, tarsi distinctly lighter. Antennomeres 1−3 light brown, 4−8 dark brown, 9−11 yellowish brown, apex of each antennomere lighter. Maxillary and labial palpi yellowish brown.

Head ( Fig 8B ). Long and narrow, 1.35 times as long as wide. Tempora straight and parallel, posterior angles rounded. Dorsal surface shiny, bearing very fine transverse microstriae and mesh, also with coarse and very sparse punctures. Head with 5−7 irregular punctures scattered around each eye and numerous smaller punctures on deflexed portion of tempus and near posterior margin. Each side of cranium with characteristic punctures: one frontal puncture on frontal region, two anterolateral punctures near antennal insertion, three lateral punctures near dorsal margin of eye, with temporal puncture and occipital puncture near basal margin; disc surface bearing two additional paired punctures in middle area. Frontal furrows and anteocular furrows absent. Eye large-sized, slightly protruding laterad, longitudinal diameter about half of length of tempora (eye: tempora = 0.48). Epistoma not flattened, abruptly oblique, anterior margin slightly emarginate medially. Ventral surface with scattered punctures, interspaces between them about 4 puncture diameters. Gular sutures deep, confluent at basal 1/4, then extended to base.

Antennae ( Fig 8C ). Scape rod-shaped, slightly thickened apically, shorter than two subsequent antennomeres combined; antennomere 2 slightly elongate, 3 distinctly longer than 2; 4 about twice the width, 4 to 10 gradually shortened, 4 observably longer than 10; 11 distinctly longer than 10.

Mouthparts. Labrum oval-shaped, lateral margin rounded, widest at basal 1/2; width of anterior margin is about half of width at widest point. Mandibles falciform, left one with three small teeth on inner margin, whereas right one with two.

Neck. Cylindrical, shiny, only bearing shallow microsculpture, shorter than 1/3 of head width. First half of dorsal surface depressed, with distinct groove. Ventral surface with gular sutures forming obvious triangular region, with deep transverse median furrow.

Prothorax ( Fig 8B ). Pronotum elongate (PL to PW ratio 1.29), distinctly longer and wider than head. Anterior region near anterior angles deflexed, lateral margins widened posteriad to basal 1/3 (widest at 1/3), then convergent backwards, anterior and posterior angles broadly rounded. Dorsal surface glossy, extensively with micropunctures, but without any microsculpture. Each side of longitudinal midline with one row of punctures composing of 3 large punctures and 2 additional punctures outside of puncture row, several punctures scatted near each margin (including anterior, lateral and posterior margins). Prosternum bearing transverse ridge between basisternum and furcasternum, angularly backwards.

Pterothorax ( Fig 8B ). Mesoscutellum triangular and small, surface shiny, bearing distinct microstriae, but without any punctures. Transverse ridge on mesoventrite wave shaped; paired oblique furrows short but deep; carina limiting mesocoxal cavity slightly arcuate. Discrimen region on metaventrite normally elevated.

Elytra ( Fig 8B ). Slightly transverse (EL to EW ratio 0.95), distinctly longer and wider than pronotum. Humeri well developed, lateral margins divergent posteriorly, hind margin not rounded, but obliquely truncate. Dorsal surface shiny, flattened, without microsculpture, finely coriaceous; each elytron with row of 5−7 punctures along suture, row of 7 punctures in median, also with 5−7 punctures on deflexed portion.

Legs ( Fig 8A ). First four segments of protarsi heart-shaped, moderately dilated, and those of meso- and metatarsi slender. Last segment of protarsi almost equal to 2−4 together, that of meso-, meta- slightly shorter than length of each 2−3.

Abdomen ( Fig 8A ). Broadest at segment V. Tergites III–VII covered with very fine shallow transverse microstriae and mesh; each tergite with dense pubescence, also with row of darker and coarser setae at posterior margin of tergites III–VI. Tergites III–VII with basal impression near anterior margin, respectively, each one only possessing one basal transverse carina; all abdominal tergites with fine and moderately dense puncturation, distance between punctures larger than diameter of puncture. Posterior margin of tergite VII with distinct palisade fringe.All abdominal sternites shiny, with microstriae and punctures as those on tergites.

Male ( Figs 8D–H ). Head with small rounded, markedly protruding elevation between eyes. Posterior margin of sternite VIII slightly emarginated medially, both sides apicolaterally shortly emarginated, before apical margin with row of about 10 short stout dark setae ( Fig 8E ). Posterior margin of tergite VIII arcuate ( Fig 8G ). Tergite IX ( Fig 8F ) symmetrical, connected mediobasally, narrowed apically. Sternite IX ( Fig 8H ) almost symmetrical, widest near basal 1/3; basal margin straight, apical margin normally emarginated. Tergite X ( Figs 8F ) symmetrical, triangular. Aedeagus ( Figs 8D ) symmetrical, large-sized, ca. 0.62 mm long, normally sclerotized. Parameres symmetrical, thick and short, about 1/6 length of median lobe. Internal structures sclerotized, two paired strips shaped sclerites located on both sides, parallel, lateral one slender, in brown color, other broader, in brown color; 3 sclerites in middle: paired rectangular sclerites in brown color, one Y-shaped sclerite in brown to black color; additional paired triangular structure near apical point. Sperm pump coiled, thinned toward apex.

Female. Unknown.

Diagnosis. Both this species and D. pubiventris have a distinctive row of thick setae along the middle apical margin of male sternite VIII ( Fig 8E , Fig 9-2E). However, in this species, these setae are significantly stouter, and the apex of sternite VIII is not strongly projected.

Distribution. Victoria.

Figures

FIGURE 8. Diochus octavii Fauvel, 1877, holotype:A. habitus, dorsal view; B. forebody, dorsal view; C. antenna; D. aedeagus, dorsal view; E. male sternite VIII; F. male tergites IX–X; G. male tergite VIII; H. male sternite IX; I. labels. (Scale bars: A–B = 0.5 mm, D–E = 0.1 mm).